Described below is an interface which relates to the technical field of electrical or electronic circuit engineering. The interface connects a converter apparatus to a two-pole line, a first pole having a higher electrical potential and the second pole having a lower electrical potential. The interface may be used in a converter system or a converter unit to connect a converter apparatus.
In Europe standards and installation guidelines in the field of automatic fire alarm technology require a fire alarm line to be protected against total failure due to a line short circuit in many applications. This requirement is currently met either by short circuit isolator elements inserted at specific points of the fire alarm line in addition to the actual sensors and actuators or by a short circuit isolator integrated in every sensor or actuator and a loop line structure. A short circuit isolator is described for example in EP 0 111 178 B1, which discloses a monitoring unit with a number of alarms linked in a chain-type manner to a loop-type alarm line, the alarms being connected to a control center with an evaluation unit. The evaluation unit can determine the nature of the operating states of the individual alarms by way of the temporal pattern of a polling voltage. A short circuit in the alarm line between two adjacent alarms can also be detected and located. Selective deactivation of the part of the alarm line in which the short circuit occurred allows the overall operating voltage to be maintained on the remainder of the alarm line.
In markets outside Europe, particularly in the United States of America, there is often no requirement to maintain the functionality of the alarm line in the event of short circuits. However the connection of a frequently very large number of sensors and actuators to such a two-pole line should be achieved as rationally and with as few possibilities for error as possible. It is therefore advantageous if the generally polarized alarm line can be connected to the devices without observing polarity. Thus for example U.S. Pat. No. 6,738,238 B2 discloses a fire alarm unit having a control center and a number of alarm devices. The alarm devices are connected to the control center by way of a two-point line, the two-point line serving both to supply power to the individual alarm devices and to signal various operating states of the individual alarm devices from the alarm devices to the control center. An alarm device is coupled to the two-point line in each instance by way of a current and signal interface which operates independently of the polarity of the respective connection. This allows the individual alarm devices to be operated independently of polarity. The current and signal interfaces each have a rectifier, which has a not inconsiderable susceptibility to noise and thus influences the operational reliability of the alarm devices disadvantageously.